Micro-electro-mechanical-system device with guard ring and method for making same

ABSTRACT

The present invention discloses a MEMS device with guard ring, and a method for making the MEMS device. The MEMS device comprises a bond pad and a sidewall surrounding and connecting with the bond pad, characterized in that the sidewall forms a guard ring by an etch-resistive material.

BACKGROUND

1. Field of Invention

The present invention relates to a micro-electro-mechanical system(MEMS) device and a method for making the MEMS device, in particular toa MEMS device with guard ring and a method for making it.

2. Description of Related Art

MEMS devices are used in a wide variety of products such asmicro-acoustical sensor, gyro-sensor, accelerometer, etc. The MEMSstructure of a MEMS device is usually located on top of the wafer, so itshould preferably be protected. The present invention thus provides aMEMS device with guard ring and a method for making it.

SUMMARY OF THE INVENTION

It is an objective of the present invention to provide a MEMS devicewith guard ring.

It is another objective of the present invention to provide a method formaking a MEMS device with guard ring.

In accordance with the foregoing and other objectives of the presentinvention, from one aspect, the present invention discloses a MEMSdevice with guard ring, comprising: a substrate including transistordevices, part of interconnection and MEMS structure; a top dielectriclayer formed on the substrate; a top metal layer, part of which formsthe bond pad; and a sidewall surrounding and connecting with the bondpad, characterized in that the sidewall is made of an etch-resistivematerial and forms a guard ring laterally sealing the top dielectriclayer.

The MEMS device may further comprise a shielding layer provided on thetop dielectric layer and connected with the sidewall. The shieldinglayer and the guard ring can each be a single layer or a compositelayer.

In another aspect, the present invention discloses a method for making aMEMS device with guard ring, comprising: providing a substrate includingtransistor devices, part of interconnection and MEMS structure; forminga top dielectric layer; forming a top metal layer, part of which forms abond pad; and forming a sidewall guard ring connected with the bond padby a material which is resistive to an etchant capable of etching thetop dielectric layer, wherein the sidewall guard ring laterally sealsthe top dielectric layer.

The method may further comprise: forming a shielding layer on the topdielectric layer and connected with the sidewall.

It is to be understood that both the foregoing general description andthe following detailed description are provided as examples, forillustration and not for limiting the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings.

FIGS. 1A-1C show an embodiment according to the present invention.

FIG. 2 shows another embodiment according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The drawings as referred to throughout the description of the presentinvention are for illustration only, but not drawn according to actualscale.

FIGS. 1A-1C shows a bond pad structure according to the first embodimentof the present invention, wherein FIG. 1B is a top view taken along theline B-B of FIG. 1A; FIG. 1C is a top view taken along the line C-C ofFIG. 1A; and FIG. 1A is a cross sectional view taken along the line A-Aof FIG. 1B. FIG. 1A shows a substrate 12 which has been processed toinclude transistor devices, part of the interconnection and MEMSstructure (not shown), and also shows a top metal layer 14 which isprovided as a bond pad on the substrate 12. The top metal layer 14 isisolated from the metal of the same level or the level beneath by a topdielectric layer 16. The top dielectric layer 16 for example can be madeof an oxide such as silicon dioxide or a low-K material containingsilicon dioxide.

The dielectric layer 16 needs to be etched during the process forforming the MEMS device. The present invention is characterized in thata guard ring 18 made of an etch-resistive material is formed as asidewall surrounding the bond pad. The guard ring 18 seals thedielectric layer 16 laterally except the open area 100. A shieldinglayer 20 is provided on top of the dielectric layer 16, which ispreferably also made of an etch-resistive material to protect thedielectric layer 16. The term “etch-resistive” means that the materialis resistive to etch of the dielectric layer 16, that is, resistive toan etchant capable of etching the dielectric layer 16.

Depending on the material of the dielectric layer 16, the guard ring 18and the shielding layer 20 can be a single or a composite layer made ofany etch-resistive material. However, the guard ring 18 and theshielding layer 20 should not be electrically connected with each other;otherwise the bond pad and the surface of the overall device will beshorted together. As long as such premise is met, the guard ring 18 canbe made of a material such as metal, amorphous silicon, silicon nitride,silicon oxynitride, or a composite material of two or more of the abovematerials, and the shielding layer 20 can be made of a material such asmetal, amorphous silicon, silicon nitride, silicon oxynitride, or acomposite material of two or more of the above materials.

FIG. 2 shows a second embodiment according to the present invention.This embodiment is characterized in that the shielding layer 20 is acomposite layer including an upper layer 20A and a lower layer 20B. Thelower layer 20B can be a layer for enhancing the adhesion between thecomposite shielding layer 20 and the substrate beneath. Or, when theguard ring 18 is made of a conductive material, one of the upper layer20A and the lower layer 20B can be made of an insulating material. Inthis embodiment, for example, the guard ring 18 can be made of amaterial such as metal, amorphous silicon, silicon nitride, siliconoxynitride, or a composite material of two or more of the abovematerials. The upper shielding layer 20A can be made of a material suchas metal, amorphous silicon, silicon nitride, silicon oxynitride, or acomposite material of two or more of the above materials. The lowershielding layer 20B can be made of a material such as metal, amorphoussilicon, silicon nitride, silicon oxynitride, or a composite material oftwo or more of the above materials. “Metal” for example can be, but notlimited to, aluminum or copper.

Although the present invention has been described in detail withreference to certain preferred embodiments thereof, the description isfor illustrative purpose and not for limiting the scope of theinvention. One skilled in this art can readily think of othermodifications and variations in light of the teaching by the presentinvention. For example, the composite shielding layer 20 can includethree or more layers. The guard ring 18 can also be made of a compositematerial. Therefore, all such modifications and variations should beinterpreted to fall within the scope of the following claims and theirequivalents.

1-8. (canceled)
 9. A method for making a MEMS device with guard ring,comprising: providing a substrate including transistor devices, part ofinterconnection and MEMS structure; forming a top dielectric layer;forming a top metal layer, part of which forms a bond pad; and forming asidewall on, surrounding and connected with the bond pad, the sidewallbeing disposed on and along all sides of the bond pad to extend upwardfrom the bond pad in a direction opposing to a downward direction fromthe bond pad toward the substrate, to form a guard ring extending upwardfrom the bond pad, wherein the sidewall is made of metal or amorphoussilicon resistive to an etchant capable of etching the top dielectriclayer, wherein the sidewall forms a guard ring; and after forming thesidewall, etching part of the top dielectric layer to release the MEMSdevice.
 10. (canceled)
 11. The method of claim 9, wherein the topdielectric layer is made of an oxide.
 12. The method of claim 9, furthercomprising: forming a shielding layer on the top dielectric layer andconnected with the sidewall.
 13. The method of claim 9, wherein theshielding layer is made of a material of metal, amorphous silicon,silicon nitride, silicon oxynitride, or a composite material of two ormore of the above materials.
 14. The method of claim 9, wherein theshielding layer is a composite layer including two or more layers, andone of the layers is made of a material of metal, amorphous silicon,silicon nitride, silicon oxynitride, or a composite material of two ormore of the above materials.